<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Descendant</title>
        <style>
            ul>li {     /*改变unordered list的子类item的样式*/
                color: blue;
            }
        </style>
    </head>
    <body>
        <ol>
            <li>list item one</li>
            <li>list item two</li>
            <ul>
                <li>sub list item one</li>
                <li>sub list item two</li>
            </ul>
            <li>list item three</li>
        </ol>
    </body>
</html>